My experience is that with the UPlanSApo 4x I can comfortably get a good stack. It is much much harder with the 10x/0.45 but still doable if the stack does not go too deep. 20x/0.75 - forget about it. I am awaiting some long working distance objectives to try out - hopefully they will give me better results.

20130517-DSLR_IMG_0001-Edit.jpg by pwnell, on Flickr
Peacock feather, 4x, Epi-LED, HF B

20130517-DSLR_IMG_0153-Edit.jpg by pwnell, on Flickr
Peacock feather, 4x, Epi-LED, HF B

20130519-DSLR_IMG_0788-Edit.jpg by pwnell, on Flickr
Peacock feather, 10x, EPI-LED, HF B (9,5)

20130519-DSLR_IMG_0958-Edit.jpg by pwnell, on Flickr
Peacock feather, 10x, EPI-LED, HF B (13,10)

20130519-DSLR_IMG_1017-Edit.jpg by pwnell, on Flickr
Peacock feather, 10x, EPI-LED, HF B (13,10)
And an extreme one with my 40/0.95 objective - not sure if it is working.

20130518-DSLR_IMG_0200-Edit.jpg by pwnell, on Flickr
Peacock feather, 40x, EPI-XC, HF B (16,8)